chtMultiRegionSimpleFoam semi-transparent solid
 

Hello everyone,

First of all I apologize for my English which is not my native language.

That's my problem. For a project, I have to manage to simulate the radiation in a semi-transparent solid in OpenFoam (version 3.0+).

For now the geometry is not important, so my geometry is simply a cube (for hot gas) with an inlet, an outlet, 3 wall and the last face is the interface between the gas my second Hexahedron which represents the semi-transparent solid (a glass).

I have already succeeded in simulating the problem without radiation and with radiation in the gas with the fvDOM model but for the solid it is more complicated. I have the impression that OpenFoam does not make it possible to simulate a solid other than opaque. :confused: Would anyone know more?

I could see on one of the posts that there existed a mode Frozenflow. So I thought to assimilate my solid to a liquid and activate Frozenflow but here is the problem, the file thermoproperties for a liquid asks to specify a viscosity and a Prandtl. However, a glass has a viscosity which tends towards the infinite and therefore a Prandtl which also tends towards infinity (because Pr = mu * cp / kappa). How can I do this?

I also tried to customize this solver but without success because my knowledge in C ++ is too limited for now. :( If the solution is towards this path, can you help me?

I thank you in advance. :)

Regards,

V.

Hello,

After carrying out some tests, I observe that the Frozenflow mode allows me to create a "solid" from a fluid.

I had the opportunity to check 2 cases. The first one where I do not take into account the radiation and I check well that the convection and conduction are identical to my case with a real solid and hot fluid. And the second case where I activate the radiation only in the hot fluid and there again I correctly check that everything corresponds to my case with a real solid.

So I decided to get to the heart of the problem, radiation in my solid semitransparent.

My first problem is to make the difference between fluid_to_solid and solid_to_fluid. For example, in the BoundaryRadiationProperties file that is located in the file constant / fluid / and constant / solid / well I do not know what difference I have to give between the 2 files.

In solid / BoundaryRadiationProperties:

boundaryField
{
". *"
{
Type boundaryRadiation;
Fashion lookup;
Emissivity uniform 0.837;
Absorptivity uniform 0.0;
Transmissivity uniform 0.9;
Value uniform 0.0; // dummy value
}

vitrage_to_gaz
{
Type boundaryRadiation;
Fashion lookup;
Emissivity uniform 0.837;
Absorptivity uniform 0.0;
Transmissivity uniform 0.9;
Value uniform 0.0; // dummy value
}

In fluid / BoundaryRadiationProperties:

boundaryField
{
". *"
{
Type boundaryRadiation;
Fashion lookup;
Emissivity uniform 0.6;
Absorptivity uniform 0.6;
Value uniform 0.0; // dummy value
}

gaz_to_vitrage
{
Type boundaryRadiation;
Fashion lookup;
Emissivity uniform 0.837;
Absorptivity uniform 0.0;
Transmissivity uniform 0.9;
Value uniform 0.0; // dummy value
}

For now I put the same thing in the 2 (the figures are those of the solid) but it seems strange to do like this because the properties of my fluid and my solid are different. So I do not know in which I have to change these numbers and insert those of the fluid.

Then, a few other questions persist and I found nothing conclusive in my research.

As I understand the code, the reflected part of a ray is reflected only diffused and not, like the Snell-Descarte theory, a reflected main ray and the rest in diffusion. Is it correct?
So, is there a way to take this into account (a main reflective ray)?

My other question is: how is the radiation transmission to the interface? Is the radiation be preserved on the other side (at the first cell at least), or is it diffused on the other side of my interface?

Your answer will allow me to tailor my problem or expand my report to explain how the problem is actually handled with OpenFoam.

Thank you in advance,

V.